My 80% lowers are shipping soon and I want to ensure I have the correct end mills on hand. I know a 2 flute works better for aluminum.  Mostly I'm curious about the best diameter and length for some of the tasks. For instance I can see where a longer end mill would be helpful for the trigger slot. Thanks

Jim

Looking for pretty specific measures of the end mill sizes so I can order what I need.

You will need a 7/16  to cut the radius's for the corners and a 5/16 for the trigger slot if you want "mill spec".  You will also need to cut 1.25" deep.  I prefer to use a 1.25" flute length and cut the whole thing with that but some people use a shorter flute length and cut to its max depth and then change to the longer mill and cut the rest.  I like the center cutting 37 degree helix in 2 flute for milling lowers.  It is designed for aluminum and it seems to cut a little better.  I can't find them in 7/16....at least reasonably priced, so I use 1/2" instead of 7/16 for the main fire control pocket.  You will also need a 3/8 drill bit for the safety, a #23 drill bit for the trigger and hammer pins, a .155, or .156 reamer and a .375 reamer.  I had everything but the reamers so I paid the $20 bucks or so for them.  If you are buying all of them and buy low to middle grade cutters, bits and reamers you will probably have close to $50 into it.  You can spend a lot more or a little less but that will give you a ball-park price.  If you have real sharp and good bits, you can get away without the reamers by using a 5/32 and a 3/8 bit.  I like to go slightly undersize and ream to size but you don't really have to.  Take your time and measure 6 times before  you cut once.  7075 can't be welded and it sucks to make a mistake...trust me.

Enco is a good source, good prices, good selection and good service all combined with fast shipping.  There are places that may be a little cheaper but it won't be by much and if you find something cheaper, they price match anyway.

I am no expert but I do a lot of metal work and have a small machine shop set up in my garage so I will answer your questions as best I can.

Dweller is right on, but I found that the 3 flute mills for aluminum worked a little better for me. It seemed like everything ran a little smoother with a little less chatter. As another source, I buy mine from McMaster-Carr.

For my benchtop CNC, 3/8" em  for FCG pocket and long-reach 1/4" em for the trigger slot.
(All radius's are compensated for in my CNC program!)
Both are 2 flute Cobalt. These cut aluminum like butter and gives an excellent Finish.
BTW...The Sharper Cobalt/HSS , will give you a better finish and require less force compared to Carbide of the same design!

I'm going to be using a Sherline. Haven't started yet. Still shopping for tools and setting up.

Scroll down to the middle of the page:

http://www.cncguns.com/tooling.html

Well,

What tooling you need or want...?

McMaster is fine, as is MSCdirect.com as well

as for the types of end mills...

i have lots of tooling for my milling machine and such...But I use a Roughing Mill for the majority of the project...

Then switch to a 2 flute and run a finishing pass...In solid carbide, Usually a 4 Inch...I have them in abundance in the shop...

i also have built them from scratch as well...And then you need a few other things...Facing mills etc...Prefer carbide insert type...

My 2 cents
Bret

I've learned which end mill not to buy, so far. Ordered some more to see if they work better.